US2367306A - Control for refrigerating apparatus - Google Patents

Description

Jan. 16, 19 45.

A. B. NEWTON CONTROL FOR REFRIGERA'IING APPARATUS Filed Aug. 1 1941 s -Sheets*$heet 1 INVENTOR Alw in. B. N'awl'om ATTORNEY Jan. 16, 1945. A. B. NEWTON I 3 CONTROL FOR REFRIGERATING APPARATUS Filed Aug. 1, 1941 3 Shuts-Sheet 2 Fig.2.

QE 9 b as r---- 7 l0 0 IO Q 0 Fig.3 Ei.4- Fig.5

' INVENTOR Alwim B. New-1:914.

ATTORNEY Jan. 16, 1945. A. B. NEWTON CONTROL FOR REFRIGERATING APPARATUS Filed Aug. 1 1941 5 Sheets-Sheet 5 Patented Jan. 16, 1945 Alwin B. Newton, Minneapolis- Minneapolis,

Honeywell APPARATUS Minneapolis, Minn., assignor to Regulator Company,

Minn., a corporation of Delaware Application August 1, 1941, Serial No. 405,032

11 Claims.

The invention herein disclosed relates primarily systems having a compressor, condenser and an evaporator connecte tionship.

One of the main objects of the invention is to provide an improved arrangement for controlling the compressor wherein the compressor is normally started in response to suction pressure but wherein there are means for starting the compressor in response to ambient temperature, the latter means being arranged to be afiected by heat-generated as an incident to operation of the system for retracting it from compressor starting position. 7

Another object is to make the temperature responsive means in the form of a timer so as to re main out of starting position of the compressor for a predetermined time to prevent it from causing short cycling of the compressor.

The ambient temperature responsive means .of the foregoing objects is particularly advantageous and desirable where the compressor is located in a relatively cold location such that the suction pressure might not rise high enough to cause the compressor to start. The heat applied to the ambient temperature responsive means causes it to move out of starting position of the compressor and to remain out of that position for a predetermined time. The controller embodying the ambient temperature responsive means may be disposed adjacent the compressor or condenser, to be heated thereby or in fulfilling another object of the invention the. necessary heat may be obtained from an electric heater.

Another object is to provide a control device, preferably a switch, for refrigerantcompressors which is normally actuated by evaporator pres-. sure or temperature but which may be actuated by an ambient temperature responsive thermostat, the latter embodying strain release means so as not to interfere with operation of the switch by evaporator pressure or temperature.

Another object is to provide a control device, preferably a switch, responsive to pressure and having bi-metal means for compensating it for ambient temperature.

Another object is to provide a compressor control arrangement comprising a switch which may be moved to on position in response to evaporator temperature or pressure provided a thermostat in the refrigerated space, is calling for cooling, the thermostat having a heater which heats the thermostat when it is satisfied to cause it to periodically cycle on and ofiso that 'oppor- 65 d in operative circuit rela- 'cation of Judson and tumty is provided for the switch to be closed by evaporator pressure or temperature at frequent intervals, the purpose of the arrangement being to provide for more uniform cycling operation.

Figure 1 represents a refrigerating system controlled by a controller embodying the ambient temperature responsive means of my invention therein, Figure 2 represents a refrigerating system controlled by a different form of controller embodying my invention,

Figure -3 represents a compressor having the controller of my invention mounted on the cylinder thereof,

Figure 4 represents a compressor and condenser with the controller mounted on the condenser,

Figure 5 represents a compressor with the controller mounted on the discharge of the compressor,

Figure 6 represents a refrigerating system embodying a form of the controller of my invention having additional means responsive to the tem- 1 perature of the refrigerated space, and

Figure '7 represents a control switch having means for compensating the switch for ambient temperature.

Referring to Figure 1 of the drawings, numeral I 0 representsthe compressor of a compression type refrigerating system. The compressor is driven by an electric motor II by means of a belt I2. The discharge side of the compressor is connected' to a condenser l3 by mean of a pipe I4, and the condenser is connected to an expansion valve l5 by means of a pipe IS. The outlet of the expansion valve I5 is connected to an evaporator I l by means of a pipe I 8. The evaporator I1 is disposed in a compartment to be refrigerated, the compartment being represented by the broken lines I 9. The outlet of the evaporator is connected to the suction side 01' the compressor, by apipe 20. p

The expansion valve I5 is a conventionaltype adapted to maintain a predetermined number of degrees of superheat of the refrigerant in the outlet of the evaporator, the valve having a pressure chamber connected by a capillary tube 2| to a thermostatic bulb 22 disposed in intimate heat exchange relation with the outlet of the evaporator.

The compressor motor I I is controlled primarily by a controller 25 which is essentially the same as the controller disclosed in detail in the appli Kronmiller, Serial No. 1938. This application 4,783 on June 10, 1941.

l 96,447, filed March 17, became Patent No. 2,24

The controller 25'operates jointly in response to head pressure and suction pressure. The controller comprises a generally rectangular casing within which is mounted an expansible and contractible bellows 26 which is connected to the suction pipe 20 by a tube 21 so as to expand and contract in accordance with-changes in suction pressure. At the movable end of the bellows 26 is a stem 29 which engages an intermediate portion of a lever '29, the lower end of which is crimped as shown and which normally engages a knife edge on a fixed member 30, the lever 29 being operable to pivot about the knife edge. The upper end of the lever 29 is attached to an adjusting screw ll extending through a sidewall of the casing of the controller 25 by means of a tension spring 32 which normally urges'the lever 29 against the stem 28. The lever 29 carries an insulating member 33 and mounted on this insulating member is a contact bracket 35 carrying an electrical contact 95 and another electrical contact 35. The contact 25 cooperates with a contact 31 carried on a flexible bracket 38 mounted within the controller 25, the mounting means forming an electrical terminal 39. The upper end of bracket 39 engages a cam 50 which acts as a stop, the cam having a gradually rising surface as shown and being mounted on a shaft 4| which extends to the exterior of the casing of. the controller 25 so that the cam can be adjusted from outside the controller. The contact 35 cooperates with a contact carried on a contact bracket 45 which is mounted within the casing of the controller, the mounting means forming an electrical terminal 51. The upper end of the bracket 45 engages a cam 48 similar to the cam 40 and which is also mounted on a separate shaft rotatable from outside the controller 25 for adjusting the cam which acts as a stop for the bracket member ll.

When the suction pressure rises, the bellows 25 expands moving the lever 29 in a clockwise direction causing contact I to be brought into engagement with contact 21 and causing contact 38 to engage contact 5 later at a higher suction pressure which may be a pressure corresponding to a temperature of 33 1". of the refrigerant in the system. As will presently be'de'scribed, the compressor is not started in operation until contact 36 engages contact 55, and inasmuch as this does not occur until the pressure of the refrigerant has risen to a value corresponding to a temperature of the refrigerant above freezing, the evaporator must defrost before the compressor can be started after the termination of the preceding cycle. When the compressor is started,

the suction pressure falls, causing the bellows 26' to contract permitting lever 29 to move in a counter-clockwise direction. When this occurs contact 36 first disengages from contact 45, and at a lower suction pressure contact 35 disengages from contact 31 and this may occur, for example, at a relatively low evaporator pressure corresponding to a temperature of the refrigerant of 15, for example. As will presently be pointed out, the compressor is not stopped until contacts 35 and 31 are disengaged. By adjusting the cams '50 and 48, the positions of the brackets 28 and 45 can be adjusted, and consequently the positions of contacts 31 and 45 can be adjusted with respect to their associated contacts to thereby adjust the suction pressures at which the contacts engage and disengage. Obviously by reason of the.

separate cams and contact brackets, the cut-in and cut-out pressures can be separately adjusted,

Numeral 50 designates a second expansible and contractible bellows within the casing of controller 25, this bellows being connected to the discharge pipe of the compressor by a tube 5!. At the movable end of bellows 50 is a stem 52 which normally engages an intermediate point of lever 53, the upper end of which is crimped and which engages a knife edge formed on a fixed member 54. The lever 53 is adapted to pivot about the knife edge on member 54 and it is normally urged in a clockwise direction into engagement with stem 52 by a coil spring 55 attached to a screw 55 extending through a sidewall of the casing of controller 25 and adjustable from outside the casing for adjusting the tension of the spring. The lower end of lever 53 carries a pusher 51 arranged to engage the lower end of contact bracket 46 when the bellows 50 expands, the contact bracket 49 extending below the terminal 41. Adjacent the lower end of bracket 46 is a contact 59 which is normally in engagement with a contact Bl) On an electrical terminal post 6|. Numeral 62 designates a contact bracket mounted within the easing of controller 25, the mounting means forming an electrical terminal 63. The bracket 62 carries a contact 54 which is normally in engagement with a contact 55 carried on an electrical terminal 59.

The pusher 51 has a shoulder 61 arranged to engage the lower end of bracket 52 when the hellows 50 expands moving the pusher 51 to the right. The purpose of the bellows 5D and its .associated contacting arrangement is to prevent lows 50 expands moving the lever 53 in a counter-clockwise direction moving the pusher 51 to the right. When the head pressure rises to pounds, for example, the end of pusher 51 engages the lower end of bracket 45 causing contact 59 to disengage from contact 60. If the head pressure continues to rise, upon further movement of pusher 51 to the right, at a somewhat higher head pressure whch may be pounds, for example, the shoulder 51 engages the lower end of bracket 62 causing contact 64 to be disengaged from contact 65. As will presently be described, in order for the Compressormotor to be started, the head pressure must have fallen to 140 pounds, but after it has been started it can be continued in operation provided the head pressure does not rise above 180 pounds.

Included within the casing of controller 25 is a relay designated by the numeral 10. The relay 10 comprises a winding 1| having an armature associated therewith which is attached to movable switch blades 12 and 13, the switch blades cooperating with fixed electrical contacts 14 and 15 respectively. When the winding 1| of the relay is energized the armature is movedin a direction to move the switch blades into engagement with their associated fixed contacts. Also mounted within the casing of the controller 25 is an overload device designated by the numeral 16 which may be of a conventional type. The overload device comprises a pair of contacts 11 and 18 which are disposed in the relay circuit, as will presently be described, and which are actuatable bya heat responsive device responsive to heat generated by an electric heater 19 in the form of a resistance connected in the load circuit, that is, in the compressor motor circuit. The overload device 16 may have a manual lever opened in response to an overload. Numerals 8| and 82 designate a pair of electrically connected terminals within the casing of controller 25.

Under some circumstances the compressor of the system ma be located in a relatively cold location, such that the suction pressure might not at times rise to a high enough value to cause closure of contacts 36 and 45 tobring aboutstarting of the compressor motor. To insure that the compressor motor may be started under such circumstances, I have provided an additional temperature responsive device responsive to the temperature in the vicinity of the compressor for starting the compressor motor even though the suction pressure does not rise high enough to close contacts 35 and 45. The temperature responsive device is mounted within the casing of controller and is designated generally by the numeral 85. It comprises a housing '86 which may be made of suitable composition,

the housing having a cover 81 which may be secured to the housing by means of a bolt 88. Within the housing is a bimetal temperature responsive element 89 carried by. bracket 98. At one end of element- 89 is an electrical contact 9| cooperating with a fixed contact 92 within the housing 86. Contacts 9| and 92 control a branch circuit arranged in parallel with contacts 35 and 45. Bearing'against an intermediate point of the element 89 is a screw 93 adjustable from outside of the housing 88 for adjustingthe spacing of contacts 9| and 92 to adjust the temperature at which the contacts will be brought into engagement. Upon a fall in temperature the lower portion of element 89 warps to the left and normally screw 93 is so adjusted that contacts 9| and 92 will be brought into engagement at a temperature of 48 F., for example. It will be understood that the controller 25 as a whole is mounted in the vicinity of the compressor so that the element 89 is responsive to the ambient temperature around the compressor. When the compressor has been started by the device 85, it may be kept in operation by other parts-of. the control mechanism and it is not desired that the compressor operate for a short period and then be immediately restarted by the device 85. Thus, after the device 85 has closed its contacts for starting the 'compressor, it is desirable that the element 89 disengage contact-9| from contact 92 relatively soon' and maintain the contacts separated for a relatively long'period of time, for example, an hour.

Thus I have constructed and arranged device. 85 so as to act as a timer to maintain the contacts openfor perhaps an hour after they have been closed to startthe compressor. The device 85 aspreviously pointed outis mounted within the casing of the controller 25. When the relay I8 is energized (energizati'ong of the relay causing operation of the compressor," as will presently be pointed out), its winding 1| generates acertain amount of heat as does the heater 19 .of

the overload device 16. The. element as of he device 85 and the other elements of the controller 25 have considerable thermal mass, and after it has closed the contacts 9| and 92, the heat generated within the controller 25 will cause the element\89 to warp in a direction to separate the contacts, and dueto the mass of the controllerifigwill accumulate a considerable amount ofthe heat generated within the controller and thisheat will maintain the device 85 in open position-of its contacts for a period of an til period, reclosure of contacts 9| and 92 will depend on the ambient temperature falling below 40 F.

To provide the necessary heating for opening contacts 9| and 92 and maintaining them open for a timed period, the controller 25 may be mounted in a position to be affected by heat generated by the refrigerating system. For instance, in Figure 3 there is shown a compressor with the controller 25 of Figure I mounted on the compressor cylinder to be heated thereby. Figure 4 shows a compressor and a condenser with the controller 25 mounted on the condenser so as to derive heat from the condenser. Figure 5 shows a compressor with the controller 25 of Figure 1-mounted on the discharge of the compressor.

The bimetal element 89 is so constructed that after the compressor has been started the heat enerated either by the controller itself, or by the compressor, or at the condenser will be sufficient to cause the element to open its contacts after approximately one minute.

While such arrangemens have not been shown, the controller may also be mounted directly on the motor, or if an air cooled condenser is used, the controller may be mounted in the stream of warm air passed over the condenser.

It will be understood ofcourse that when the compressor is started in operation the ambient temperature surrounding it will rise, and this rise in temperature will also tend to keep the device in open position. Qf course after the compressor has stopped and after the expiration of the timing period, the ambient temperature will have fallen back to normal, and as pointed out above reclosure of contacts.9| and 92 will depend upon the ambient temperature falling below 40 F. 4

The controls for the compressor motor include a thermostat 99 in the refrigerated compartment l9. The thermostat 99 comprises an expansible and contractible bellows |88 having a stem engaging a pivoted lever |8|. The lever |8| carries a mercury switch I82 having electrodes at its left end. When the temperature in the refrigerated in a clockwise direction into a position wherein mercury switch I82 is opened. In other words, the ther fiiostat as has a differential of 2' F.

- In normal operation, the compressor motor II will be started when the mercury switch. I82 closes indicating a need for refrigeration in the compartment I9, provided all of the contacts responsive to suction and head pressure within the controller 25 are closed. In other words, the

head pressure must be below 148 pounds to prevent overloading of the compressor motor upon starting and the suction pressure must have risen to-a value high enough to have caused defrosting of the evaporator. I When the above conditions prevails circuit is completed for the relay III as follows? from wire I05 to terminal 66 through contacts 65 and 60, contact bracket 62, terminal 63, wire I06, mercury switch I02, wire I01, termimi 38, contact bracket 38, contacts 31 and 35, contact bracket 30, contacts 36 and 05, contact bracket 86, contacts 59 and 60, terminal 6I, wire I08, wire I09, contacts 11 and I8, wire IIO, winding II, wire III, terminals 82 and 8| to wire H2. The wires I05 and H2 may be connected to any suitable source of power not shown. When the winding II of relay I is thus energized the switchblades I2 and 13 are moved into engagement with their respective contacts. Engagement of blade I2 with contact II completes a maintaining circuit for relay winding II which by-passes suction pressure contacts 36 and and head pressure contacts 59 and 60 so that after the relay is energized it will be kept energized through the maintaining circuit even though the suction pressure falls below the value at which contacts 36 and 05 close and even though the head pressure rises above 140 pounds.

' The maintaining circuit is as follows; from wire I05 to terminal 66, contacts 65 and 64, contact bracket 62, terminal 63, wire I06, mercury switch I02, wire I01, terminal 39, contact bracket 38, contacts 31 and 35, contact bracket 34, wire II3, wire III, contact 14, switch blade I2, wire 5, wire I09, contacts 11 and I8, wire IIO, winding 1I, wire III, terminals 82 and 8I back to wire II 2.

Engagement of switch blade I3 with-contact 15 completes a circuit energizing the compressor motor as follows: from wire I05 to terminal 66, wire I I6, to overload heater I9, wire III', contact I5, switch blade 13, wire Ill, compressor motor II, wire II9, terminals 82 and 8| back to wire H2. The relay I0 remains energized keeping the compressor in operation until either the suction pressure falls to the value at which contacts 35 and 31 open so as to interrupt the above described maintaining circuit or until the said maintaining circuit is interrupted by opening of mercury switch I02 in the event of thermostat 89 becoming satisfied. The maintaining circuit may also be interrupted in the event that head pressure rises above 180 pounds causing contacts 60 and 85 to become separated. Normally, however, the relay 10 will be deenergized to terminate an operating cycle either in response to suction pressure or in response to the thermostat 99.

As pointed out above, under some circumstances when the compressor is in a relatively cold location wherein the suction pressure might not rise high enough to cause contacts 38 and to close for energizing the relay, it is necessary rely on other means for causing the compressormotor to start. As pointed out above, the con-' troller 25 is located in the vicinity of the compressor so that the device 85 is responsive to the ambient temperature surrounding the compressor, and this device is set to normally close its contacts at a temperature of 40 F'., this temperature being exemplary of one below which the air surrounding the compressor would be so-cold that the suction pressure would not rise high enough to close contacts 36 and 85. When the device 85 closes its contacts, a circuit is completed which energizes the relay I0, this circuit by-passing contacts 36 and 05 and being as follows: from wire I05 to terminal 66, contacts 65 mercury switch I02, wire I01, terminal 39, contact bracket 38, contacts 31 and 35, contact bracket 34, wire 3, wire I2 0, wire I2I, contacts 92 and 9I, element 89, wire I22, terminal 41, contact bracket 46, contacts 59 and 60, terminal 6|, wire I08, wire I09, contacts 11 and I6, wire IIO, winding II, wire III, terminals 82 and 8| back to wire II2. Completion of this circuit energizes relay I0 causing starting of the compressor motor, as described above, and also causing completion of the above described maintaining circuit through the thermostat 99, it being understood, of course, from the circuit just described, that the thermostat 99 must be in a position demanding refrigeration in order for the device 85 to start the compressor motor.

When the relay is energized and the compressor motor started the heat generated by the heater I9 and the relay winding are suilicient to cause the element 89 to separate the contacts 9| and 92 substantially one minute after they have closed. Or if the controller 25 is mounted in one of the positions previously described, the heat from the compressor or condenser serves to cause the device 85 to open its contacts. After the device 85 opens its contacts, the compressor motor is kept in operation, however, through the maintaining circuit and it will continue to operate until the maintaining circuit is interrupted either by the suction pressure opening contacts 35 and 31 or the temperature in the refrigerated compartment causing the thermostat 99 to become satisfied. While the compressor is in operation, the controller 25 accumulates additional heat tending to keep contacts 9| and 92 separated. As before, of course, the maintaining circuit may be opened by reason of the head pressure rising above pounds. Thus after the compressor motor has been started by the device 85 it will operate for a length of time depending both upon what the suction pressure was at the time the compressor was started and upon the temperature in the refrigerated space. It the suction pressure has risen only slightly above the value at which contacts 35 and 3'! closed at the time the compressor motor is started in response to the device 85, the compressor motor will be operated only for a very short time, that is, until the suction pressure is reduced suillciently to open the contacts 35. and 31.

Afterjthe compressor motor has been started by the device 85 and has then been stopped by one o! the other control means, it is not desired that the compressor motor be started to recycle the system immediately or after a very short delay. Therefore the device 85 has the function of a timing device so that its contact will not become closed for a period of substantially an hour after the compressor motor has been stopped. During the time that the compressor motor is operating, the controller 25 will accumulate a certain amount of heat which is generated. within the controller 25 or as has already been described this heat may be provided by the compressor motor or condenser when the controller 25 is mounted in one of the positions shown in Figs. 3 to 5. The heat which the various parts of the controller .will absorb is suflicient to raise its temperature a given amount, and after the compressor motor has been stopped and the air in the vicinity of the compressor cools back to normal substantially one hour of time will be required for the controller 25 to dissipate its accumand 6 ta t bracket 8 t rm n l ll, e Ill.%1s ulated heat and to permit element as to again respond normally to the. normal ambient tem-' perature surrounding the compressor. Thus, the arrangement provides for starting the compressor motor even though the normal control responsive to suction pressure will not do so. Short and frequent cycles are prevented by reason of the timing function which the device 85 has which provides for substantially an hours delay after stopping of the compressor motor before it can again be started by the device 95.

Those skilled in the art will appreciate the advantages of my improved arrangement inasmuch as it insures starting of the compressor motor when necessary but will not start the com pressor motor at other times. The device utilized is very simple in construction and utilizes heat already available in the system.

The invention may be carried out by closing contacts 9! and 92 by means of a thermal bulb and bellows arrangement, the bulb being mounted on the compressor discharge pipe or other place where it will be heated when the system is in operation.

Referring to Figure 2 of the drawings, I have shown a refrigeration system which is the same as the one disclosed in Figure 1, this system being provided with a different form of controller embodying the compressor starting means of my invention, that is, the means responsive to the ambient temperature around the compressor. In Figure 2 the system itself is the same as in Figure l. and the elements thereof are numbered the same.

Thecontrollerof Figure 2 comprises a casing E25 having a horizontal shelf I26 therein and mounted on the shelf I26 is a snap switch generally designated by the numeral I21, the snap switch being enclosed within a Bakelite housing and being of the same type as disclosed in detail in the application of A. E. Baak, Serial No. 307; 991, filed December 7, 1939. The switch I21 has on and off positions and is of the type adapted to remain in the position to which it is operated, the switch having a downwardly extending operating stem designated by the numeral I 28. Numeral I29 designates an operating lever, the right end of which engages in a slot in the stem I28 and the left end of which is disposed between two cams I39 and BI which act as stops for the lever I29. The cam I39 has' a generally rising contour and is mounted on a shaft extending through a sidewall of the casing I25, the shaft being rotatable .by knob I32 outside of the casing for adjusting the position of the cam. The cam I3I similarly has a generally rising contour and this cam also is mounted on a shaft which extends through a sidewall of the casing of the controller I25, this shaft being rotatable by knob I33 outside of the controller for adjusting the position of cam I3 I.

Numeral I35 designates a housing attached to the exterior of the casing of controller I25, there being an expansible and contractible bellows III) within the housing I35. The interior of the ML lows is connected to the suction pipe of the compressor by a tube I36. The movable end of the bellows is connected to an operating stem I31 which extends through a fitting I38 into the interior of the casing of controller I and the end of the stem I31 carries a ball I 39 disposed loosely in an opening at an intermediate point in the -lever I29. Numeral I40 designates a leaf spring attached to the upper side of lever I29 and en-, 1 gaging the ball I39. Numeral I4I designat similar leaf spring attached to the lower ide of lever I29 and also engaging the ball I39, the stem I31 passing through the leaf spring MI. The leaf springs I40 and MI by reason of their engagement with the ball I39 provide a strain release connection between the stem I31 and the lever I29 to permit relative movement between the stem I31 and lever I29.

Numeral I42" designates a screw extending through the shelf I26 above the lever I29 and directly in line with the stem I31. The strain release n-echanism comprising the leaf spring I40 normally does not engage the screw I42 in operation. The purpose of the screw will presently be described.

In normal operation the switch I21 maybe opened and closed inresponse to changes in suction pressure. Thus, upon a rise in suction pressure the bellows within housing I35 is expanded against the force of a spring included in the bellows assembly causing the stern I31 to be moved upwardly until the left end of lever I29 engages the cam I39. This occurs at a predetermined relatively high suction pressure which is normally one high enough to insure that the evaporator has defrosted, and when this occurs the lever E29 pivots in a counter-clockwise direction about the cam I as a fulcrum moving the stem I28 upwardly, which movement closes the switch I21. When the switch. I21 closes, a circuit is completed to the compressor motor, as will presently be described, for starting the compressor motor which causes the suction pressure to fall. The point in the movement of stem I 3? at which the end of lever I29 engages cam E39 and thus the pressure at which switch E21 is closed may be adjusted by adjusting the cam E39. This of course following from the fact that the cam I30, as pointed out above, has a gradually rising surface.

When the suction pressure falls, the bellows within housing I collapses moving lever I29 downwardly until its left end engages cam Iiil. This occurs at a predetermined relatively low suction pressure determined by the adjustment of cam I3I, and when it does occur the lever S29 is movedin a clockwise direction moving the operating stem I28 downwardly and opening the switch H1. The point in the movement of stem I31 at which the lever I29 engages cam HI and consequently the pressure at which switch I21 is opened is adjustable by adjusting the cam I3I, the cam having a gradually rising surface as pointed out above.

The strain release connection between the stem I31 and the lever I29 provides a release for the force exerted by the bellows if the bellows should continue to expand or contract after the end of the lever I 29 has engaged one of the cams and'has thereby operated the switch I21.

As in the previous embodiment of the invention, the compressor may be located in a locality wherein the temperature is so low that the suction pressure may not rise high enough to cause closure of the switch I21 for starting the compressor. To insure that the switch I21 will be closed when there is a need for refrigeration even though the suction pressure-does not rise high enough to close the switch, I have provided a thermostatic device generally designated at I45. The device I45 comprises a coiled bimetal element I44, the inner end of which is attached to a rotatable pin I46'carrying an arm I41. The arm I41 is normally urged into engagement with a. screw I 48 carried by abracket I49 by means of a coil spring I50. The other end of the elemeat I44 carries a finger II adapted to engage the end of the operating stem I28. The element I44 contracts upon rising temperature, and when the temperature in the vicinity of the compressor is high enough so that the switch I21 can be closed by suction pressure, for example, when the temperature is above 50 F., the finger I5I normally does not engage the stem I28. When the temperature in the vicinity of the compressor falls so low however, that suction pressure does not rise high enough to close the switch I21, for instance, when the temperature surrounding the compressor ialls into a range of from F. to 50 F., for example, the element I44 will expand, moving finger I5I into engagement with the stem I28 and at a predetermined temperature moving the stem upwardly so as to close the switch I21 for starting the compressor. When the finger I5] is thus engaging the stem I28 the switch I21 may be opened in response to suction pressure at substantially the same value as normally by reason oi the strain release arrangement formed by the arm I41 and spring I50. Thus, it finger I5I is engaging the stem I28, the stem I28 may be moved downwardly by the lever I29 in response to a fall in suction pressure. When this occurs the stem I28 moves the finger I5I downwardly, and under these circumstances bodily rotating the element I44 and arm I41 against the force of spring I58. The force exerted by sprin I58 is relatively small and does not add appreciably to the downward force which the right end of lever I28 must exert to move the stem I28 downwardly for opening switch I21. The forces required to actuate switch I21 are relatively small, and of course when the device I45 closes the switch I21 the force exerted by finger I5I against the stern I28 is less than the force exerted by spring I58, the arm I41 under these circumstances remaining in engagement with the screw I48.

The device I45 may, if desired, be formed and arranged to act as a timer as in the previous embodiment. Thus the controller I25 may be mounted in any of the positions shown in Fi ures 3 to 5 so that when the compressor is started the element I44 will be heated so as to move finger I5I out of engagement with stem I28. In those forms of my invention wherein the device I45 is constructed to act as a timer as well, the controller has enough thermal mass so as to accumulate a certain amount of heat while the compressor is operating. This heat raises the temperature of the controller a given amount and aiter the compressor has stopped and the air in the vicinity thereof cools to its normal value substantially an hour, for example, is required for it to dissipate its accumulated heat and to again respond normally to ambient temperature.

If it is not desired to mount the controller I25 in any of the positions shown in Figures 3 to 5,

an auxiliary heater I54 may be provided to heat the element I44 when the switch I21 is closed. The heater I54 is connected in series with the switch I21 as will presently be described so as to cause the device I45 to be heated during the time. that the compressor is in operation.

Numeral I55 designates a thermostat oi the on" and 011" type which is located in the compartment to be refrigerated and which closes its contacts at a predetermined value of temperature in the refrigerated compartment, these contacts being in series with the switch I21.

In normal operation the compressor motor is started when the thermostat I has its contacts closed indicating a need for refrigeration, and when the switch I21 is closed in response to suetion pressure in the manner above described. When this occurs, a circuit for the compressor motor II is completed as iollows: from wire I56 to thermostat I55, wire I51 to a terminal of switch I21, through switch I21 to its other terminal. wire I59, heater I54, wire I68, motor II to wire IBI, the wires I56 and IGI being connected to any suitable source of power not shown. When the compressor motor is started the suction pressure falls and the motor operates until the above described circuit is interrupted either by thermostat, I55 or by opening of switch I21 in response to suction pressure. During the time that the compressor motor is operating the heater I54 opens the element I44 maintaining the finger I5I out of engagement with the stem I28.

Under some circumstances it may be desirable to operate the compressor motor solely from the thermostat I55 with the controller I25 acting only as a low pressure cutout requiring manual reset. To provide for this type of operation. the switch I21 is manually closed and the screw I42 is screwed downwardly far enough so that the lever I29 is prevented from being raised high enough to engage the cam IBIJ and cause closure of switch I21 in response to suction pressure. Under these circumstances the switch I21 normally remains closed and the compressor is started and stopped in response to the thermostat I55 alone, the Lhermostat I55 normally becoming satisfied and stopping the compressor motor before the switch Itl is opened in response to falling suction pressure.

However, with this type oi. operation, if the suction pressure does fall to the relatively low value determined by the setting of the cam I3 I, the lever I25 will be actuated to open the switch I21 and stop the compressor motor. If this occurs, the switch I21 will remain open until it is manu ally reclosed, since screw I42 prevents upward movement of lever I29. It is to be seen therefore that with screw I42 adjusted as described above for this type of operation, the controller I25 acts as a low pressure cut-out requiring manual reset.

When the ambient temperature surrounding the compressor falls into the range between 35 F. and 50 F., the suction pressure will not rise high enough to cause closure of switch I21 for normal operation. Under these circumstances at a predetermined ambient temperature, the device I45 will cause finger I5I to engage the stem I28 and close switch I21 as above described. When the switch I21 is thus closed, if thermostat I55 is calling for refrigeration at the time, the above described circuit for heater I54 and compressor motor II will be completed. When the compressor is thus started, heat either from the compressor itself, or from the condenser if the controller I25 is mounted as shown in Figures 3 to 5, or heat from the heater I54 if it is used.

will cause the element I44 to move the finger I51 away from the stem I28; As described above, after the compressor motor has stopped, substantially an hour will be required for the controller I25 to dissipate its accumulated hent after which element I44 will again respond normally to ambient temperature.

From the foregoing, it is to be understood that the present embodiment of the invention provides for substantially the same type and sequence of operation as obtained in the previous embodiment, the present embodiment utilizing a difi'erout form of controller.

Referring to Figure 6 of the drawings, I have shown a modified form of my invention embodied in a system, the system being the same as that shown in Figures 1 and 2 having its elements numbered'the same.

ments of the controller I25 of Figure 2 are num-' In Figure 6 the ambient tembered the same. perature responsive device comprises a bimetal element I66, the inner end of which is rigidly secured to the casing of the controller I65 and the other end of which is adapted to engage operating stem I28 of the snap switch I21 and to close the switch when the temperature within the casing of controller I65 falls to a predetermined value within a range in this modification of the invention of from 55 F. to 70 F. This temperature range within the casing of the controller corresponds to an ambient temperature range around the compressor of from 35 F. to 50 F. as will presently be explained.

The controller I includes an electromagnetic device designated generally at I81, this device being controlled by the' thermostat 99 in the refrigerated compartment, this thermostat being the same as that of Figure l but having an electric heater 408 associated therewith, the purpose of which will presently be described. In the controller Hi5 the switch it? is supported ona shelf I60 which has an angular bracket portion, as shown, which carries and supports an electrical winding Hi3 forming part of the electromagnetic device iiil. Within thawinding H0 is a core Elli which cooperates with an armature 12 in the form of a lever which is pivoted to the bracket portion of the shelf I69 and which is normally biased a clockwise direction by a coil spring E13 which is attached to the left end of lever I12 and to the bracket portion of shelf 69. When the winding HI! is not energized the spring 13 urges the lever 12 in a clockwise direction causing the right end of the lever' I 12 to engage the lever I29 so as to urge the latter lever downwardly in a manner to maintain the stem I28 in a downward position with the switch I21 open. With the partsof the controller I65 in the position shown in Figure 6, the suction pressure is normally inoperative to close the switch I21 by reason of the spring I13 and lever I12. However, with the parts in this position the suction pressure is eflective to close the switch provided the suction pressure rises to a higher than normal value sufiicient to overcome the force of spring I13, this higher than normal value ofcourse depending upon the spring I13.

The winding I is normally connected to a power source in series with the electrical heating resistance I68. The circuit is as follows: from a line conductor I1! to wire I15, winding I10, wire I15, wire I11, electrical resistance. I08,

wire I18, wire I19 to line conductor I00, the line conductors I14 and I80 being connected tothe power source. The circuit for I10 iust described is not sui'ficient to cause the armature of the electromagnetic device to be attracted; it remains in the position shown. The circuit of winding I10 energizes it sufllciently to cause it to generate a. certainamount of heat and this circuit through the electrical. resistance I08 causes it to give off a certain amount of heat to .heat 'the' thermostat 99. The thermostat 80 in the present modification may have a, diilerential of 2 F., for example; that is, it may close the mercury switch I02 at 42 F. and open it at F. The resistance I68 may be such as to [produce 3 of heat, for example; that is, it may raise the temperature in the refrigerated compartment locally around the thermostat 3 such that when the temperature within the refrigerated compartment is at 39 F. or above this value, with the mercury switch I02 open, the heat from resistance I68 will heat the thermostat sufiiciently to cause it to close the mercury switch I02. When the mercury switch I02 closes, an additional circuit is completed for winding I10 which shunts the heater I68, this circuit being as follows: from line conductor E14, through wire I15, winding I10, wire E16, wire I8I, mercury switch I02, wire I 82, wire I10 back to line conductor I80. The latter circuit places winding I10 directly across the line. The latter circuit carries suihcient current so as to energize the electromagnetic device I61 sufficiently to cause its armature to be attracted, that is, the lever I12 is rotated in a counter-clockwise direction against the force of spring I13 and is held in its rotated position. With the parts so response tosuctionpressure and the switch I21 may under these circumstances be closed in response to suction pressure at the normal cut-in pressure. When lever I12 has been moved away from lever H9, as soon as the suction pressure rises to the cut-in value, the switch E21 will be closed for starting the compressor and as in the previous embodiments the cut-in pressure is preferably high enough to insure that the evaporator has defrosted in the meantime. The circuit for the compressor is as follows: from line, conductor H t through wire IE5, compressor motor H, wire E86, switch E21 through wire E81 back to line conductor I80. When the compressor is started, the suction pressure is ofcourse reduced and the operating cycle proceeds normally.

Operation of the system of course tends to reduce the temperature in the refrigerated compartment I9 and with the heater 568 not now energized the thermostat 99 will respond to the actual temperature in the refrigerated compartment, and whenever this temperature is reduced below 40 F., the thermostat 99 will open its switch I024 deenergizing the last described circuit for winding I10 and causing the'original circuit through I68 to be reenergized. Interruption of the circuit through mercury switch [02 will cause the electromagnetic device I61 to assume 1 the position shown in Figure 6, the lever I12 acting on lever I29 to open the switch I21 terminating- When thethermostat 9! becomes satisfied as above described, the heater I60 becomes reener sized so as to heat the thermostat to cause it to again assume unsatisfied position. In this manner it is to be seen that normally the therpositioned, the lever I29 is not restrained from normal operation in mostat 99 will cycle on and off by reason of heater I68 so as to cause the device I61 to intermittently per-mit closing of switch I21 in response to suction pressure. In the present form of the invention the thermostat 99 normally cycles on and off approximately every ten minutes. That is approximately ten minutes of operation of the compressor are required for switch I02 to open and the heater closes it in a half minute, for example. By reason of the cycling operation of thermostat 99, opportunities are provided at frequent intervals for the switch I21 to be closed in response to suction pressure, and after the compressor has been thus started its operation. is not prolonged but it is terminated whenever the thermostat 99 becomes satisfied. Thus, the opei ration provides for relatively short and frequent cycles 01 the compressor which operation is de sirable particularly under light load conditions to prevent the humidity within the refrigerated compartment from rising too high such as would occur if there were long off periods of the coinpressor. The more frequent compresso (JIM-llations resulting from the use of the heater type thermostat prevents the occurrence of such long off periods of the compressor and thus the humish ity is kept within a desired The current flow through the wine through the above described circuits winding to generate a. certain amoi which normally will maintain. i within the controller IE5 at above the ambient 'tempei-atuil reason that the element Hill is arrahijred to c mately higher than the tacit element I66 responded directl temperature. When the ambi above the range of from to '1 there is no need tor closing the switch by means of the element Itii, the heat generated within the controller 155 keeps the free end of the element IE6 disengagedfrom the stem Hit The element I66 expands in response to falling tern perature and when the ambient temperature falls into the range just mentioned, that is, the range between 35 F. and F. the free end of the element I66 will engage the operating stem I28 at a predetermined temperature within the casing of controller I65 and will close the switch I21 for starting the compressor. This operation is substantially the same as that described in connection with the previous embodiment. The tern-- perature at which the switch I 21 is closed by the element I66 will be substantially 20 higher than the ambient temperature as explained above. By reason of the frequent cycling of the thermostat 99 and the electromagnetic device I61, the temperature within the casing of. controller I65 is normally maintained at substantially 20 above the ambient temperature as described, that is, winding I 10 is practically continuously energized. Without the heater in combination with the thermostat 99 the device I61 would not be so frequently energized and the temperature within the casing of the controller I65 would not be as constant. Under such circumstances upon energizatlon of the device I61 the temperature within the casing of controller I65 would rise to a value above normal and this rise in temperature would prevent the device I56 from closing the switch I21. Thus the heater type thermostat 99 cooperates with the control device I to enable the ambient thermostat I66 to start the compressor,

at the proper value of ambient temperature and C" "UPI iii to be otherwise disengaged from the operating stem I28 0! the switch I21.

From the foregoing it will be apparent to those skilled in the art that in the present embodiment of the invention I have provided an arrangement wherein the compressor is started in response to suction pressure and in response to the thermostat in the refrigerated compartment and is stopped either when the temperature in the refrigerated switch in response to ambient tempo ure. The elements of the controller oi? lgure l e essentially identical with those 0 controller of liigure 2 and they numbered 1c. The

controller oi Figure l however eludes bowed bin'ietal element to ambient tempei star The lot eleroaent is a! and the o abuttin the s or ed, w

.utioli lly inonsive thC l causing the i .1 r value oi suction 1 the onlioller were not compeus bieiit temperature. lvhen the suc is l'allins: and the lever tilt is being moved down wardly by the stem ltll the element lilil resists such downward movement depending upon the temperature affecting the element lllil and thus makes fit-necessary for the suction pressure to fall to a lower than normal value in order for the switch i ll to be opened. The element I eirpends upon falling temperature and contracts upon rising temperature; that is, it warps in a direction to urge the lever I29 upwardly'with greater force when the ambient temperature falls. The element I90 is so arranged that when the ambient temperature is above 50 F., it exerts negligible force upon the lever I29 so as to not affect the cut-in and cut-out points of the controller. When the ambient temperature falls into a range of from 35 F. to 50 F.. such that the suction pressure may not normally rise high enough to cause closure of the switch I21, the element I90 effectively compenstates the cut-in and cut-out points of the switch I21 as above described, the element lowering both the cut-in and cut-out points of the switch.

The embodiments of my invention which I have disclosed and described in detail are representative of its preferred forms. There are various modifications and variations which may be made in the invention but which fall within its spirit and scope. My disclosure is therefore to be interpreted in an illustrative rather than a limiting sense and the invention is to be limited only in accordance with the claims appended hereto.

I claim as my invention:

1. In a refrigerating system; a compressor; an

evaporator; and control mechanism for controlling said compressor comprising a device movable between positions for starting and stopping the compressor, means responsive to a condition which is a measure of evaporator temperature for actuating saiddevice, means responsive to temperature of the refrigerated space having on and off positions for moving said device to one of its positions when said temperature responsive means is in a given one of its positions, said temperature responsive means being arranged to resist movement of said device out of said one position as long as the temperature responsive means remains in said given one of its positions, and means arranged to change the temperature of said temperature responsive means when it assumes said given position so as to cause it to assume its other position.

2. In a refrigerating system; a compressor; an

evaporator; and control mechanism for said system comprising a device movable between positions for starting and stopping the compressor, means responsive to a condition which is a measure of evaporator temperature for actuating said device, means responsive to temperature of the refrigerated space arranged to resist movement of said device out of 011 position for the compressor whenever said temperature responsive means is satisfied, and means to heat said temperature responsive means when satisfied so as to cause said latter means to assume an unsatisfied position wherein said device is not resisted from movin out of off position for the compressor whereby said temperature responsive means operates'in a periodic cycling manner to periodically remove the resistance it offers to movement of said device to starting position for the compressor in response to said condition responsive means.

' 3. In a refrigerating system; acompressor; an evaporator; and control mechanism for said system comprising a device movable between positions for starting and stopping the compressor, means responsive to a condition which is a measure of evaporator temperature [for actuating said device, means responsive to temperature of the refrigerated space having on and of! positions for moving said device to one of its positions when said temperature responsive means is in a given one of its positions, said temperature responsive means being arranged to resist movement of said device out of said one position as long as the temperature responsive means re-. -mains in said given one of its positions, said temperature responsive means including meansadapted to generate heat near said device, temperature responsive means arranged to be influenced by a relatively low temperature in the vicinity of the compressor for moving saiddeure of evaporator temperature for actuating said device, means responsive to temperature of the refrigerated space having on and off positions for moving said device to one of its positions when said temperature responsive means is in a iven one of its positions, said temperature re-- sponsive means being arranged to resist movemeat of said device out of said one position as long as the temperature responsive means remains in said given one of its positions, said temperature responsive means including an electrical mechanism adapted to generate a substan- V the vicinity of the compressor for moving said.

device into starting position for the compressor, said last temperature responsive means being so located as to be subjected to said generated heat whereby the device is normally not operated thereby unless the said relatively low temperature in the vicinity of the compressor is reached.

5. A'refrigeration system comprising in combination, a compressor and evaporator, switch means in control of said compressor and located in the vicinity of said compressor, means transmitting pressure from the suction line of said refrigeration system to said switch for closing the same upon an increase in suction pressure, and means responsive to the temperature at said switch for decreasing the value of suction pressure at which. said switchis closed upon a decrease in said temperature.

6. A refrigeration system comprising in combination, a compressor and evaporator, switch means in control of said compressor and located in the vicinity of said compressor, means transmitting pressure from the suction line of said refrigeration system to said switch for closing the same upon an increase in suction pressure, means responsive to the temperature at said switch for decreasing the value of suction pressure at which said switch is closed upon a decrease in said temperature, and means preventing closure of said switch except when there is a demand for refrigeration.

7. In a refrigerating system having a low pressure side and a high pressure side, in combination; a translating means for circulating refrigerant from said low pressure side to said high pressure side; and means for controlling the operation of said translating means including a unitary control mechanism, said control mechanism including means responsive to low side pressure, means operated by said pressure responsive 7 means for normally deenergizing said translating means when said pressure is below a certain value, means emitting heat when said translating means is energized, and means responsive to the temperature of said mechanism as a whole for causing energization of said translating 'ture of said mechanism as a whole above said means when the temperature of said mechanism is below a predetermined value even though said pressure is below said certain value, said mechanism being so constructed that theheat from said emitting means raises the temperameans.

8. In a refrigerating system having a low pressure side and a high pressure side, in combination; a compressor for circulating refrigerant from said low pressure side to said high pressure side; and means for controlling the operation of said compressor including a unitary mechanism, said mechanism'being located in proximity to said compressor and comprising means for controlling the energization of said compressor, means indicative of the pressure of said low pressure side for energizing said compressor when said pressure reaches a relatively high value, means emitting heat when said compressor is operating,

said mechanism being capable of being warmed as a whole by said heat above a predetermined temperature value and having heat capacity, and means responsive to the temperature of said mechanism as a whole eflective, when said temperature is below said predetermined value, to cause energization of said compressor although said pressure is below said relatively high value,

said temperature responsive means being inefIec-' tive to influence energization of the compressor when the temperature or said mechanism is above said predetermined value.

9. In a refrigerating system having a suction pressure side and a high pressure side, in combination; a compressor for circulating reiriger ant from said suction pressure side to said high pressure side; an electric motor for driving said compressor; an energizing circuit for said motor; and a unitary control mechanism, said mechanism including a relay for controlling said circuit, suction pressure responsive means, first and second switch means operated by said suction pressure responsive means, means responsive to the temperature of said mechanism as a whole, additional switch means operated by said temperature responsive means, an energizing circuit for said relay including said first and second switch means, said first switch means being operated when-the suctionpressure is above a relatively low value, said second switch means being operated when said suction pressure reaches a relatively high value, and a branch of the relay energizing circuit for making said additional switch means operative in parallel with said second switch means, said additional switch means being operated when the temperature of the mechanism as a whole is below a predetermined value. said relay emitting heat when energized, said mechanism having heat capacity such that, when warmed due to energizing of said relay, a period of time is required for the temperature of the mechanism to fall sufiiciently, after deenergizing said relay, to again cause operation of said additional switch means.

,10. A refrigerating system comprising, in combination: a refrigerant flow circuit having a high pressure side and a low pressure side; a compressor for pumping refrigerant from said low pressure side to said high pressure side; and a unitary control mechanism including switch means in control of said compressor, means responsive to pressure in said low pressure side for closing said switch means upon an increase in said pressure, means responsive to the temperature of said mechanism as a whole effective to decrease the value of low side pressure required to close said switch means when said temperature is below a predetermined value, said mechanism having heat capacity, and means for sufliciently heating said mechanism as a whole when said compressor is being operated to render said temperature responsive means ineffective to influence the pressure required to operate said switch means, said temperature responsive means remaining inefiective after operation of the compressor is stopped for the period of time required for said mechanism as a whole to cool below said predetermined temperature.

11. A refrigerating system comprising, in combination: a refrigerant flow circuit having a high pressure side and a low pressure side; a com pressor for pumping refrigerant from said low pressure side to said high pressure side; an electric motor for driving said compressor; an electrical circuit for energizing said motor; a first switch for controlling the operation of said motor; and a control mechanism including a second switch for controlling said motor, said first and second switches being connected in series in said electrical circuit, said mechanism including a floating lever, means responsive to said low side pressure operatively connected to an intermediate portion of said lever, said second switch being operatively connected to a second portion of said lever whereby said switch may be operated by said lever, a pair of stops for limiting motion of a third portion of said lever, the values of low side pressure at which said second switch is opened and closed being determined by said stops, said mechanism also including temperature responsive means operating on said second switch means when the temperature of said mechanism as a whole is below a predetermined value in a manner to reduce the value of the low side pressure required to close said second switch, said temperature responsive means being ineffective to influence said second switch when the temperature of said mechanism as a whole is above said predetermined value, and means heating said mechanism during operating periods of said compressor,.the heat absorbed by said mechanism being capable of maintaining said temperature responsive means ineffective for a period of time after said compressor stops, said period of time depending on the cooling time of said mechanism.

ALWIN B. NEWTON.

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